1. Technical Field
The present invention relates to an oscillation module, and an electronic apparatus and a vehicle each equipped with the oscillation module.
2. Related Art
In JP-A-2004-040509 (Document 1), there is disclosed an oscillation circuit constituted by an oscillating differential amplifier formed of an ECL line receiver, a differential amplifier for a feedback buffer, which is formed of an ECL line receiver, and has an output terminal terminated with an emitter termination resistance, a switch circuit, a voltage-controlled phase-shift circuit, an SAW resonator, and an impedance circuit, and in the oscillation circuit, there is formed a positive feedback oscillation loop constituted by at least the oscillating differential amplifier, the differential amplifier for the feedback buffer, the voltage-controlled phase-shift circuit, and the SAW resonator. According to the oscillation circuit, by varying the emitter termination resistance of the differential amplifier for the feedback buffer to increase the drive level of the SAW resonator, the amplitude of a signal from the SAW resonator becomes relatively larger compared to the noise to be superimposed on that signal. In other words, since the high SN ratio can be achieved, the jitter due to the noise superimposed on the signal from the SAW resonator can be reduced.
Although the oscillator circuit outputs the oscillation signal with a frequency in the vicinity of the resonance frequency of the SAW resonator, it is also possible to oscillate a signal with a frequency N times of the resonance frequency by providing a multiplier circuit in the posterior stage. In, for example, JP-A-2007-013565 (Document 2), there is disclosed an oscillation circuit having a multiplier circuit disposed in the posterior stage of a ring oscillator. The multiplier circuit has a configuration of outputting an exclusive OR of two signals taken out from any two stages of inverters out of odd number of stages of inverters constituting the ring oscillator, and if, for example, the multiplier circuit described in Document 2 is disposed in the posterior stage of the oscillator circuit described in Document 1, it is possible to obtain a multiplied output while suppressing an increase in the circuit area.
The oscillation circuit has a configuration of outputting the oscillation signal with the frequency in the vicinity of the resonance frequency of the SAW resonator and the oscillation signal with the frequency obtained by multiplying the frequency in the vicinity of the resonance frequency of the SAW resonator, but has a room for improvement regarding the change in the frequency band of the oscillation frequency using the master slice.